Ruling a blow to Bonds prosecution

In a 21-page opinion issued late Thursday, U.S. District Court Judge Susan Illston made a series of rulings that will prevent federal prosecutors from using positive drug tests and other important evidence in the upcoming trial of Barry Bonds on perjury charges. Illston's rulings raise significant legal questions about the prosecution's case and its future. Here are some of the questions and their answers:

What are the effects of Judge Illston's rulings?

The rulings are devastating setbacks for prosecutors who have been investigating Bonds and preparing for a trial that is scheduled to begin March 2. A substantial portion of the government's evidence will never be shown to the jury, leaving the prosecution on life support. The judge rejected the government's clever and creative arguments for the use of drug tests, drug calendars and logs and a tape-recorded statement from Bonds' trainer. Her rulings leave the government with a difficult task, relying on thin circumstantial evidence of Bonds' physical changes and some expert testimony.

What can the government do?

Judge Ilston's rulings have sparked a debate among the prosecutors in San Francisco. Should they appeal her adverse rulings? Should they appeal in an effort to salvage the powerful evidence that Ilston has barred? Should they risk losing an appeal that could result in precedents that would hurt prosecutors throughout the U.S.? They must decide within a few days. They are legally entitled to an appeal. After obtaining approval for the appeal from senior officials at the U.S. Department of Justice in Washington, they can ask for a review from the U.S. Court of Appeals. If the prosecutors file the appeal, the high court must examine each of Ilston's rulings and determine whether it is correct. The only requirement for the appeal is a statement from the U.S. Attorney in San Francisco, Joseph P. Russoniello, that the appeal is not for delay but instead involves rulings on evidence "of a fact material" to the issues in the trial.

What happens to the trial if the prosecutors appeal Illston's rulings?

The trial would probably be delayed indefinitely. It would be highly unusual for Illston to start the trial with the appeal pending and unresolved. Steven A. Miller, a former federal prosecutor in Chicago, said, "It would be extremely bad form for the judge to proceed with the trial if there is an appeal involving important pieces of evidence."

If the government does not appeal, what will happen?

The trial would begin March 2. The government would still attempt to persuade jurors that Bonds is guilty of perjury and obstruction of justice, but prosecutors would have a difficult time. Some portions of the testimony from Kimberly Bell, Bonds' former girlfriend, might even be barred at the trial. Judge Illston is still deciding whether to permit the prosecutors to show that Bonds' body changed in major ways as the result of performance-enhancing drugs. Bell must submit her testimony in written form before Feb. 24 to preserve any hope that the jury will hear what she has to offer. There is so little left of the government's evidence after Illston's rulings that the trial could end unexpectedly early. If the government fails to produce enough evidence to make what is known as a prima facie case, the trial could come to an end. At the conclusion of the government's evidence, the Bonds defense team would make a motion to end the trial. The Bonds lawyers would argue that there is not even enough evidence to allow the jury to decide. The legal term is a "directed verdict," and it is now a real possibility.

How did this happen after nearly five years of government effort focused on BALCO and Bonds?

Bonds can thank his trainer, Greg Anderson, for these rulings. Anderson's steadfast refusals to testify before the grand jury that investigated Bonds, and his unwillingness to testify in the upcoming trial, left the government with gaps in its evidence that, so far, the prosecutors have been unable to fill. Bonds' defense strategy is totally dependent on Anderson and his refusal to testify against Bonds, and it is, for now, working beyond even the expectations of Bonds' legal team. Although many legal experts reviewed the evidence and concluded that prosecutors had found avenues around the Anderson testimony, Judge Illston has refused to accept any of the government suggestions.

Lester Munson, a Chicago lawyer and journalist who reports on investigative and legal issues in the sports industry, is a senior writer for ESPN.com.